1. Field of the Invention
The present invention relates generally to a method and apparatus for managing radio resources in a mobile communication system, and more particularly, to a method and apparatus for periodically transmitting information about the availability of radio resources for a current network from a base station to a mobile terminal, thereby allocating the radio resources efficiently.
2. Description of the Related Art
FIG. 1 illustrates a radio resource allocation procedure between a base station and a mobile terminal in a conventional mobile communication system.
Referring to FIG. 1, for call establishment, a mobile terminal 100 transmits a Packet Channel Request to a base station 102 via a Random Access Channel (RACH) to request allocation of radio resources (step 110).
When the base station 102 is capable of allocating radio resources to the mobile terminal 100, the base station 102 transmits a Packet Uplink Assignment to the mobile terminal 100 to allocate radio resources to the mobile terminal 100 (step 118).
However, when the base station 102 is busy and hence there are no radio resources available to the mobile terminal 100, the base station 102 transmits a Packet Queuing Notification to the mobile station to request the mobile station to wait temporarily (step 112).
Thereafter, when a Timing Advance (TA) calculated by the base station 102 at the receipt of the radio resource allocation request changes due to the movement of the mobile terminal 100, the base station 102 transmits a Packet Polling Request to the mobile terminal 100 to update the TA (step 114). Upon receipt of the Packet Polling Request, the mobile terminal 100 transmits a Packet Control Acknowledgement to the base station 102 (step 116). The TA update process may be performed depending on the type of a base station.
When the network state of the base station 102 becomes capable of allocating radio resources to the mobile terminal 100, the base station 102 transmits the Packet Uplink Assignment to the mobile terminal 100 to allocate radio resources to the mobile terminal 100 (step 118).
As described above, the mobile terminal of the conventional mobile communication system does not know about the availability state of radio resources. Therefore, although the base station is busy and hence there are no radio resources available to the mobile terminal, the mobile terminal requests the base station to allocate radio resources via the RACH, which increases a network load. Moreover, there is a high probability that the RACH used by the mobile terminal for the radio resource allocation request is transmitted with the same random number and on the same frame as another RACH that can be normally processed by the base station, causing a collision between the respective RACHs. In addition, there is a case where the mobile terminal transmits a resource allocation request to a base station, which does not perform the TA update process, receives a temporary wait request from the base station, and is then allocated radio resources after long-distance movement. In this case, the TA information changes and thus a collision occurs against a burst using an adjacent time slot during uplink transmission, which necessitates the mobile terminal to restart the resource request process.